1. Field of the Invention
The present invention relates to hybrid cables, a process for obtaining such and a composite fabric usable in a tire incorporating said cables. The invention also relates to a tire and a mounted assembly which each incorporate such a composite fabric.
2. Description of the Related Art
The development of tires intended to be fitted on passenger vehicles of the type which travel at high speeds has given rise to increasingly high-performance architectures being developed for these tires.
One solution conventionally used for these “high-speed” tire architectures consists of covering the working crown plies of these tires, which comprise metallic or textile reinforcement elements, with what is called a hooping crown ply, usually reinforced by textile cables. This hooping crown ply, which is for example arranged radially to the outside of the crown reinforcement of the tire, is in particular characterized in that the cables which reinforce it are arranged in a spiral at an angle of 0° or close to 0° with the median circumferential plane of the tire. It is also known to arrange relatively narrow strips or plies at an angle of approximately 0° instead of the aforementioned cables, in order to fulfil a hooping function of the crown reinforcement.
Hybrid cables of plied-yarn type, which are formed of two threads based on materials of low and high initial moduli respectively which are twisted together, in order to impart to the cable thus obtained a tensile modulus which is reduced at low deformation and on the contrary high at high deformation have in the past been tested as textile cables for hooping crown plies. This decoupling of the tensile moduli of the cable results in the presence of a transition point on the force/elongation curve of said cable, and it is for example obtained using a polyamide 6,6 for the material of low modulus and aramid for the material of high initial modulus.
For the description of such hybrid cables, reference may be made to US patent specification U.S. Pat. No. 3,977,172 and to the proceedings of the conference Kautschuk+Gummi Kunststoffe, vol. 40, No. 2, February 1987, pages 130–135, in Heidelberg (Germany), E. R. Barron, entitled “Hybrid tire cords containing kevlar® aramid”.
One major drawback of these hybrid cables having a plied-yarn structure is the excessive hooping tension of the ply comprising these cables, including at reduced speeds typically less than 120 km/h, (i.e., at relatively low deformations). This tension or premature “stiffening” of the cables results in a running noise due to the tire which is significant at these speeds, which represents a significant source of discomfort for the occupants of the vehicle.